1. Technical Field of the Invention
The invention relates to a dosing inhaler, consisting of an active liquid container, which contains a liquid having an active substance dissolved therein, and an atomizer, by means of which the liquid can be transformed into an aerosol and introduced into an aerosol dome, in which a baffle plate is arranged, and to which a supply-air tube and an exhaust-air tube are connected, and an electronic control.
2. Description of the Prior Art
The inhalation of active substances that are dissolved in water and inhaled as a fine mist has long been well known as a method of administering active substances, particularly in the medical field. The finer the droplets, the greater is the proportion that is transported deep into the lung with the respiratory air. In the prior art, a mist is generated by means of an ultrasonic oscillator. It is either arranged on the base of the vessel with the active liquid, and generates on the surface of said liquid a spray that isolates a mist so fine that it behaves as smoke and can therefore be easily entrained with the air stream. It is necessary that, to separate out aerosol droplets larger than about 10 microns, the air stream must be diverted at least twice. To this end, a baffle plate is arranged above the ultrasonic spray. A downwardly open, hollow truncated cone has been found most effective. The droplets rise into this truncated cone and are set into turbulence in the centre of the cone, the larger drops being removed from the mist and falling backing into the active liquid container. Only the very finest drops are entrained with the air stream and transported around the edge of the baffle either via a narrow slit or through calibrated openings into the exhaust air channel. At this point, further undesirably large droplets are separated out.
Particularly efficient is the principle of active substance transport into the lung by means of an aerosol, as a result of the very small droplets that are possible with ultrasonic atomizers. It can be proven that droplets below a minimum size are completely absorbed into the lung sacs and transferred to the blood.
However, a severe weakness is the exact dosage of the active substance. Though it is also a principal advantage of inhalation that, in comparison to all other methods of administration of drugs, very small amounts, in absolute terms, are required, it is primarily only a psychological problem that, of the active liquid, a residue of the order of single-digit percentages remains in the active substance container. If the amount falls below this minimum quantity, the ultrasonic oscillation no longer generates a spray and also does not form water droplets any longer.
However, this minimum amount can be calculated in advance with good accuracy and therefore only the dosage to be administered can be added.
With the exact dosage of the active substance amount actually absorbed by the patient, according to the prior art, the most serious problem is the patient's respiratory behaviour, which can be neither monitored nor controlled with the equipment known in the prior art. Unlike oral administration—in which an unwilling and/or debilitated and/or unconcentrated patient either takes the medication dose completely, or doesn't take it at all, however it is only in a practically negligible number of cases that he accidentally takes a partial dose—with the inhalers of the prior art, it is very often the case that only a part of the active substance dose transformed into the aerosol is actually taken by the patient. The rest is either transformed from the aerosol state back into a liquid, or, because of insufficient air velocity, is deposited in the tube systems of the inhaler or only passes as far as the patient's mouth/throat area. In simple devices without supply air and respiratory valve, it can also occur that the patient does not inhale the aerosol, but also blows it out of the device into the environment.